Methods for the preparation of the spirostanic analogues of brassinosteroids (25R)-5alfa- spirostan-6-one-2alfa,3alfa-diol and (25R)-B-homo-5alfa-spirostan-6-oxo-7-oxalactone- 2alfa,3alfa-diol, starting from diosgenin, were examined. The best preparative route was via diosgenin tosylation, isosteroidal rearrangement with potassium acetate in aqueous acetone, oxidation with Jones reagent, cyclopropyl ring opening with hydrobromic acid, hydrogen bromide elimination with lithium bromide and carbonate, dihydroxylation with osmium tetroxide and N-methylmorpholine N-oxide, producing (25R)-5alfa- spirostan-6-one-2alfa,3alfa-diol in 57.3% overall yield and lactonization with trifluoroperoxyacetic acid producing (25R)-B-homo-5alfa-spirostan-6-oxo-7-oxalactone- 2alfa,3alfa-diol in 24.6% overall yield from diosgenin. The shortest route to (25R)-5alfa-spirostan-6-one-2alfa,3alfa-diol results in only 39.4% overall yield.
We have developed polyclonal antibodies against the brassinosteroid, 24-epicastasterone. Antiserum against this substance was produced by immunizing rabbits and mice with 24-epicastasterone O-(carboxymethyl)oxime (24-epiCS-CMO) conjugated with bovine-serum albumin (BSA). The conjugates were prepared by a mixed anhydride procedure. The antibodies obtained were tested in enzyme-linked immunosorbent assay (ELISA) using 24-epiCS-CMO-peroxidase conjugate. The use of the ELISAallowed detection over the range of 0.01 to 500 pmoles. Natural brassinosteroids (BRs) like brassinolide, and 24-epibrassinolide exhibited relatively high cross-reactivities but many other natural BRs were inactive. The 24-epiCS-CMO ligand was also slightly active in second bean internode bioasaay and on cancer cell lines of different histopathological origin.
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